There is a strong trend in the field of low voltage DC/DC converters for computers and communication systems towards higher load currents. Increased load current requirements most often are addressed by the interleaved synchronous multi-phase converters. It is very important for reliability of synchronous multi-phase converters that all phases share the load equally. Inequality in phase currents results in increased current draw from the corresponding input rail above the current normally associated with load demand. The increased current substantially increasing power dissipation in active and passive components effectively reducing overall system efficiency and reliability. Also, it is often of major importance to some computer and communication systems to have the ability to scale the system capabilities by using several similar or identical converters in parallel which further extends design requirements for load current sharing to an inter-module level.
DC/DC converters that employ conventional current-mode control inherently provide some degree of spreading the load current between the phases and from module to module. However, conventional current-mode systems operating over a wide range of input voltage have limited current feedback to avoid a sub-harmonic oscillation which tends to limit achievable current equity. Also, conventional solutions do not provide a means to actively share the current between several modules.
In contrast, DC/DC converters that employ conventional voltage-mode control require special circuitry for processing phase current related signals to derive corrective signals that in turn alter the duty factor of each phase. In conventional voltage-mode systems, a high performance error amplifier with high bandwidth is typically required to boost the phase at frequencies higher than the converter's control loop crossover frequency which presents design challenges typically having extensive cost associated therewith. These design challenges are exacerbated in multi-module systems. Additionally, the voltage mode converters inherently have deprived response to the input voltage step which limits their applicability.
Therefore, there is a need for a multi-phase power system employing an innovative control scheme for distributing the load current between system channels without compromising small signal response and input voltage step response. Furthermore, for power systems comprised of several multi-phase power modules, it would be advantageous to provide load sharing not only between the phases within a single module but between the modules as well.